King of the Hill (1997)

S12E19 Strangeness on a Train

Feeling anxious that her birthday celebrations never meet her hopes, Peggy organizes a disco-themed party aboard a mystery train. When Luanne accidentally spills the beans about the surprise, Peggy becomes concerned that her parties are doomed to fail. Yet, a new intrigue unfolds when a couple sneaks off for some alone time in the train’s restroom, prompting the guests to unravel the mystery of what happened.